When Galaxies Collide

A new article in the July issue of Sky and Telescope mentions that
about
several billion years in the future, the Andromeda Galaxy will collide
with the Milky Way. When that happens it seems feasible that both
galaxies may merge to form a large elliptical galaxy, with the merged
galaxy potentially forming an active galactic nucleus. An active
galactic
nucleus could potentially be a quasar, or at least some other very
bright object producing large amounts of radiation from the infall
of gas and dust, into the merged black hole, originating from both
galaxies.

Large elliptical galaxies are generally noted for very little gas and
dust within them, producing virtually no new star formation. It has
been conjectured that this is because very active galactic nuclei
deriving from the infall of gas and dust into the supermassive black
holes in the past produced radiation pressure from the central
infall region, blowing all of the gas and dust out of the galaxy,
perhaps in a slightly similar way to the ignition of a star also,
sometimes blowing off the infalling gas and dust that may initially
be forming it in a nebula. Many galaxies also have central
regions with no star formation, also speculated to be caused
by active galactic nuclei very early in their formation, blowing
gas and dust away from the central regions. If the active galactic
nuclei are less violent or negligable, there might be areas of
gas and dust outward from the central bulge that then forms
stars later, like the spiral arms of the Milky Way, with some
if its later generation, metal rich stars.

Two basic questions:

1. When the Andromeda and Milky Way collide several billion
years in the future, how severe will be the radiation source
from an active galactic nucleus that could potentially form
from the merger? Would all of the gas and dust from both
galaxies be blown off into intergalactic space, totally ending
star formation in both galaxies, or would there still be a
few areas at the far periphery that could still form stars?

Could a collision of Andromeda with the Triangulum Galaxy
potentially have any effects on the Milky Way, and when
will that happen, if it happens?

If there were life bearing plants in the merging galaxies at
that later period in time, would it be enough to snuff out
any potential life on such worlds? If a planet nearly identical
to Earth with Earth-like life were situated 10,000, 30,000,
50,000, or 100,000 light years from the merged cores of
both galaxies, would it produce virtually no changes to
any life or civilizations on any of those worlds, or would
it be enough to totally destroy life on a wide number of
them?

and 2. (mainly for alt.history.future)

If by that time, both the Milky Way and the Andromeda
galaxies had trans-galactic civilizations in both of them,
would it be possible, useing known physics, to prevent
the formation of an active galactic nucleus, from the
merger, if for no other reason to preserve the existance
of star forming regions in both of them?

What sort of engineering feats would be required to prevent
the infall of gas and dust into two merging supermassive
black holes? Would this be an engineering feat physically
impossible, even to two-trans galactic civilizations potentially
spanning, millions or even billions of stars, several billion
years in our future?

Orbitan wrote:
A new article in the July issue of Sky and Telescope mentions that
about
several billion years in the future, the Andromeda Galaxy will collide
with the Milky Way. When that happens it seems feasible that both
galaxies may merge to form a large elliptical galaxy, with the merged
galaxy potentially forming an active galactic nucleus. An active
galactic
nucleus could potentially be a quasar, or at least some other very
bright object producing large amounts of radiation from the infall
of gas and dust, into the merged black hole, originating from both
galaxies.

Large elliptical galaxies are generally noted for very little gas and
dust within them, producing virtually no new star formation. It has
been conjectured that this is because very active galactic nuclei
deriving from the infall of gas and dust into the supermassive black
holes in the past produced radiation pressure from the central
infall region, blowing all of the gas and dust out of the galaxy,
perhaps in a slightly similar way to the ignition of a star also,
sometimes blowing off the infalling gas and dust that may initially
be forming it in a nebula. Many galaxies also have central
regions with no star formation, also speculated to be caused
by active galactic nuclei very early in their formation, blowing
gas and dust away from the central regions. If the active galactic
nuclei are less violent or negligable, there might be areas of
gas and dust outward from the central bulge that then forms
stars later, like the spiral arms of the Milky Way, with some
if its later generation, metal rich stars.

Two basic questions:

1. When the Andromeda and Milky Way collide several billion
years in the future, how severe will be the radiation source
from an active galactic nucleus that could potentially form
from the merger? Would all of the gas and dust from both
galaxies be blown off into intergalactic space, totally ending
star formation in both galaxies, or would there still be a
few areas at the far periphery that could still form stars?

Could a collision of Andromeda with the Triangulum Galaxy
potentially have any effects on the Milky Way, and when
will that happen, if it happens?

If there were life bearing plants in the merging galaxies at
that later period in time, would it be enough to snuff out
any potential life on such worlds? If a planet nearly identical
to Earth with Earth-like life were situated 10,000, 30,000,
50,000, or 100,000 light years from the merged cores of
both galaxies, would it produce virtually no changes to
any life or civilizations on any of those worlds, or would
it be enough to totally destroy life on a wide number of
them?

and 2. (mainly for alt.history.future)

If by that time, both the Milky Way and the Andromeda
galaxies had trans-galactic civilizations in both of them,
would it be possible, useing known physics, to prevent
the formation of an active galactic nucleus, from the
merger, if for no other reason to preserve the existance
of star forming regions in both of them?

What sort of engineering feats would be required to prevent
the infall of gas and dust into two merging supermassive
black holes? Would this be an engineering feat physically
impossible, even to two-trans galactic civilizations potentially
spanning, millions or even billions of stars, several billion
years in our future?

I would think that just the extreme stellar-level gravitational chaos of a
galactic collision would send stars and their planets out of their orbits and
off in all sorts of diections, quickly killing whatever life they may harbor.

--
___________________________________________ ____ _______________
Regards, | |\ ____
| | | | |\
Michael G. Koerner May they | | | | | | rise again!
Appleton, Wisconsin USA | | | | | |
___________________________________________ | | | | | | _______________

Orbital wrote:

A new article in the July issue of Sky and Telescope mentions that
about
several billion years in the future, the Andromeda Galaxy will collide
with the Milky Way.

Actually, any such article is almost certainly wrong.

Although we might measure the line of sight velocity of
the Andromeda galaxy (and even the interpretation of that
is subject to dispute by Arp and others), we cannot measure
the radial motion accurately. This means that even if they
are moving towards each other they will highly likely miss.
In so doing they would orbit endlessly and not hit.

--
Ray Tomes
http://ray.tomes.biz/
http://www.cyclesresearchinstitute.org/

In article , Ray Tomes
wrote:

Orbital wrote:

A new article in the July issue of Sky and Telescope mentions that
about
several billion years in the future, the Andromeda Galaxy will collide
with the Milky Way.

Actually, any such article is almost certainly wrong.

Although we might measure the line of sight velocity of
the Andromeda galaxy (and even the interpretation of that
is subject to dispute by Arp and others), we cannot measure
the radial motion accurately. This means that even if they
are moving towards each other they will highly likely miss.
In so doing they would orbit endlessly and not hit.

Um isn't the Radial velocity the line of sight one. The proper,
tangential motion is the one we cannot measure properly. Redshift can
be measured quite well, and that gives us a measure of the radial
velocity via Hubble.

--
The true enemy of science is psuedoscience...

....
several billion years in the future, the Andromeda Galaxy will collide
with the Milky Way.
Actually, any such article is almost certainly wrong.

Actually, the people who work in this field are quite competent. They
look at detailed radio maps of the streamers of gas around galaxies in
detail and so on; they examine a good deal of evidence beyond simple
redshift. This is not my particular field but I've had a course in
galactic dynamics and it is not full of simple-minded people - if the
experts in the field did predict a collision and/or merger - and I know
they were talking about this ten years ago - then they are very likely
right, within whatever error bars they give.


Although we might measure the line of sight velocity of
the Andromeda galaxy (and even the interpretation of that
is subject to dispute by Arp and others), we cannot measure
the radial motion accurately.

Um isn't the Radial velocity the line of sight one. The proper,
tangential motion is the one we cannot measure properly.

Second poster is correct, I assume the first poster just made a typo.
The first poster has a good point that redshift alone is insufficient
to predict a collision; my point is that the people who work in
galactic dynamics examine many kinds of evidence before making
predictions.

Is there a what-if here?

Orbitan wrote:
A new article in the July issue of Sky and Telescope mentions that
about
several billion years in the future, the Andromeda Galaxy will collide
with the Milky Way. When that happens it seems feasible that both
galaxies may merge to form a large elliptical galaxy, with the merged
galaxy potentially forming an active galactic nucleus. An active
galactic
nucleus could potentially be a quasar, or at least some other very
bright object producing large amounts of radiation from the infall
of gas and dust, into the merged black hole, originating from both
galaxies.

Large elliptical galaxies are generally noted for very little gas and
dust within them, producing virtually no new star formation. It has
been conjectured that this is because very active galactic nuclei
deriving from the infall of gas and dust into the supermassive black
holes in the past produced radiation pressure from the central
infall region, blowing all of the gas and dust out of the galaxy,
perhaps in a slightly similar way to the ignition of a star also,
sometimes blowing off the infalling gas and dust that may initially
be forming it in a nebula. Many galaxies also have central
regions with no star formation, also speculated to be caused
by active galactic nuclei very early in their formation, blowing
gas and dust away from the central regions. If the active galactic
nuclei are less violent or negligable, there might be areas of
gas and dust outward from the central bulge that then forms
stars later, like the spiral arms of the Milky Way, with some
if its later generation, metal rich stars.

Two basic questions:

1. When the Andromeda and Milky Way collide several billion
years in the future, how severe will be the radiation source
from an active galactic nucleus that could potentially form
from the merger? Would all of the gas and dust from both
galaxies be blown off into intergalactic space, totally ending
star formation in both galaxies, or would there still be a
few areas at the far periphery that could still form stars?

Could a collision of Andromeda with the Triangulum Galaxy
potentially have any effects on the Milky Way, and when
will that happen, if it happens?

If there were life bearing plants in the merging galaxies at
that later period in time, would it be enough to snuff out
any potential life on such worlds? If a planet nearly identical
to Earth with Earth-like life were situated 10,000, 30,000,
50,000, or 100,000 light years from the merged cores of
both galaxies, would it produce virtually no changes to
any life or civilizations on any of those worlds, or would
it be enough to totally destroy life on a wide number of
them?

and 2. (mainly for alt.history.future)

If by that time, both the Milky Way and the Andromeda
galaxies had trans-galactic civilizations in both of them,
would it be possible, useing known physics, to prevent
the formation of an active galactic nucleus, from the
merger, if for no other reason to preserve the existance
of star forming regions in both of them?

What sort of engineering feats would be required to prevent
the infall of gas and dust into two merging supermassive
black holes? Would this be an engineering feat physically
impossible, even to two-trans galactic civilizations potentially
spanning, millions or even billions of stars, several billion
years in our future?


http://www.public.iastate.edu/~astro...cts/curt2.html
http://nedwww.ipac.caltech.edu/level...as/frames.html
http://edu-observatory.org/eo/galaxies.html

2006-06-02 .com,
paulaireilly wrote:
Second poster is correct, I assume the first poster just made a typo.
The first poster has a good point that redshift alone is insufficient
to predict a collision; my point is that the people who work in
galactic dynamics examine many kinds of evidence before making
predictions.

But galaxies aren't solid - I've read online about estimates on the
number of star-star collisions that a galactic collision would entail.
Some such estimates have been as high as a dozen.

Jordan Abel wrote:
2006-06-02 .com,
paulaireilly wrote:
Second poster is correct, I assume the first poster just made a typo.
The first poster has a good point that redshift alone is insufficient
to predict a collision; my point is that the people who work in
galactic dynamics examine many kinds of evidence before making
predictions.

But galaxies aren't solid - I've read online about estimates on the
number of star-star collisions that a galactic collision would entail.
Some such estimates have been as high as a dozen.

Galaxies are very far from solid, but a galactic collision does several
things.

1. Galaxies are typically far from virialized. The relaxation time for
stellar orbits in a galaxy of even moderate size are orders of
magnitude greater than the age of the Universe. I.e., there is a great
deal of "structure" in galaxies, even elliptical galaxies. When two
galaxies collide, these structures are changed. Typically a small
number of stars are thrown out at high speed, and the remainder tend to
collapse toward the new core. It is believed that the new structure
tends to settle down toward 'elliptical' or giant elliptical. Giant
ellipticals often have several dense areas in their cores - it is
thought these may each be centered on large (millions+ of solar masses)
black holes, which probably came from the cores of galaxies that merged
to form the giant ellipticals. We cannot wait and see this process
happening, but we can see many galaxies in various stages of this
process of collision and merger, and do simulations that look a good
deal like what we see around us.

2. Galaxies, especially spirals and irregulars, have a good deal of gas
in them. Gas clouds DO collide, with shock waves, heating, star
formation, and so on. Galactic collisions and mergers are not merely
gravitational events; they are violent because these clouds hit at high
speeds (hundreds of kilometers per second) and a great deal of energy
is released. This is why galactic collisions can look spectacular. The
colliding gas clouds are brilliant in certain regions of the spectrum,
and trigger star formation, including giant young stars that are
brilliant in visible light.

Is there a what-if here? Why is this not in an astronomy group? I am
not sure how to redirect followups.

Ray Tomes wrote:

Actually, any such article is almost certainly wrong.

Although we might measure the line of sight velocity of
the Andromeda galaxy (and even the interpretation of that
is subject to dispute by Arp and others), we cannot measure
the radial motion accurately. This means that even if they
are moving towards each other they will highly likely miss.
In so doing they would orbit endlessly and not hit.


Arp and others have been discredited for some time in such claims. And,
more importantly, their claims are for objects such as quasars, not
nearby galaxies such as the Andromeda galaxy. The distance to it has
much smaller error bars based on multiple overlapping distance tests
(distance determined by using Cepheid variables and other methods, not
Hubble expansion). So, your reliance on anything they say to support
your own claim is bogus.

More to the point, radial velocity measurements provide line of sight
measurements of motion. What you are likely attempting to talk about is
tangential velocity, that is, motion across the line of sight. At this
time, the Andromeda galaxy is far enough away from us that it shows no
proper motion, which can be translated into tangential velocity knowing
the distance to it.

So, what you more properly should have said is that there is no
knowledge of its total velocity (tangential and radial), so it could
miss. As to orbiting endlessly, this is not likely as they are mutually
pulling on each other and will eventually collide. Whether it will
happen in about 3 billion years or not remains to be determined.

Most simulations showing a direct impact show them passing through each
other and merging at an even later date. Those passes may eventually
strip much of the remaining gas from each or cause that gas to be
compressed enough to create a burst of star formation, using it up.
Also it is likely that such a pass will likely jettison stars from each
into the space surrounding them.

Orbitan wrote:
A new article in the July issue of Sky and Telescope mentions that
about
several billion years in the future, the Andromeda Galaxy will collide
with the Milky Way. When that happens it seems feasible that both
galaxies may merge to form a large elliptical galaxy, with the merged
galaxy potentially forming an active galactic nucleus. An active
galactic
nucleus could potentially be a quasar, or at least some other very
bright object producing large amounts of radiation from the infall
of gas and dust, into the merged black hole, originating from both
galaxies.

Large elliptical galaxies are generally noted for very little gas and
dust within them, producing virtually no new star formation. It has
been conjectured that this is because very active galactic nuclei
deriving from the infall of gas and dust into the supermassive black
holes in the past produced radiation pressure from the central
infall region, blowing all of the gas and dust out of the galaxy,
perhaps in a slightly similar way to the ignition of a star also,
sometimes blowing off the infalling gas and dust that may initially
be forming it in a nebula. Many galaxies also have central
regions with no star formation, also speculated to be caused
by active galactic nuclei very early in their formation, blowing
gas and dust away from the central regions. If the active galactic
nuclei are less violent or negligable, there might be areas of
gas and dust outward from the central bulge that then forms
stars later, like the spiral arms of the Milky Way, with some
if its later generation, metal rich stars.

Two basic questions:

1. When the Andromeda and Milky Way collide several billion
years in the future, how severe will be the radiation source
from an active galactic nucleus that could potentially form
from the merger? Would all of the gas and dust from both
galaxies be blown off into intergalactic space, totally ending
star formation in both galaxies, or would there still be a
few areas at the far periphery that could still form stars?

Could a collision of Andromeda with the Triangulum Galaxy
potentially have any effects on the Milky Way, and when
will that happen, if it happens?

If there were life bearing plants in the merging galaxies at
that later period in time, would it be enough to snuff out
any potential life on such worlds? If a planet nearly identical
to Earth with Earth-like life were situated 10,000, 30,000,
50,000, or 100,000 light years from the merged cores of
both galaxies, would it produce virtually no changes to
any life or civilizations on any of those worlds, or would
it be enough to totally destroy life on a wide number of
them?

The chances are that any life on a planet wouldn't
even know the galaxies are colliding.



and 2. (mainly for alt.history.future)

If by that time, both the Milky Way and the Andromeda
galaxies had trans-galactic civilizations in both of them,
would it be possible, useing known physics, to prevent
the formation of an active galactic nucleus, from the
merger, if for no other reason to preserve the existance
of star forming regions in both of them?

No, since the "known" laws of physics of
galaxies are actually unknown laws of dark matter.



What sort of engineering feats would be required to prevent
the infall of gas and dust into two merging supermassive
black holes? Would this be an engineering feat physically
impossible, even to two-trans galactic civilizations potentially
spanning, millions or even billions of stars, several billion
years in our future?